Nuclear reactors with water-basin or pool cooling are known. The heat produced in the reactor is conducted by natural circulation to cooling elements, which transfer it to customers or to the environment. Some of these reactors have high, promptly negative neutron-absorption temperature coefficients. This means that removal of the neutron-absorbing control rods results in only a limited power excursion, since the temperature increase automatically limits the chain reaction.
Nuclear reactors in which the power is regulated by varying the content of neutron-absorbing solutions in the coolant, which also acts as a moderator, are known.
Nuclear reactors are known in which the spent fuel elements are individually manipulated and successively placed in transport containers, in which they assume an adequately subcritical configuration so that they can be transported.
Nuclear reactors are known in which the pressure drop via the reactor core, which is cooled by forced circulation, is in equilibrium with the hydrostatic negative pressure under a gas-filled bell in such a way that any disruption in cooling causes the gas to escape and the core to be flooded with neutron-absorbing water from the basin (i.e., pool).